Wales's injury problems are increasing ahead of their Six Nations opener in Dublin on Sunday. Already facing the prospect of missing seven of the players who started last October's World Cup quarter-final against Ireland, they will be without the hooker Matthew Rees, who missed out on going to New Zealand because he needed an operation on his neck.

Rees, who would have captained Wales in the World Cup, would probably only have been on the bench at the Aviva Stadium, given the form of his replacement, Huw Bennett, in the tournament, but the calf injury he sustained in training this week means that Wales, already without the prop Gethin Jenkins and the lock Alun Wyn Jones, have lost three tight forwards who have led their country.

Wales's strong showing in the World Cup was due, in part, to the way they married experience with youth, but they face an imbalance at the start of the Six Nations with the second-row Luke Charteris out for the whole tournament, the wing Shane Williams having retired from international rugby and the centre Jamie Roberts among three players facing fitness tests before Friday's team announcement.

The back-row Dan Lydiate and the fly-half Rhys Priestland are the others. None has yet played a full part in training this week and the Wales kicking coach, Neil Jenkins, said on Wednesday that it was too early to say whether any of the three would make the starting lineup.

"We hope they all recover, but whether they do is a matter of time," he said. "We will have a good idea of where we stand by Thursday. The three were in and out of Tuesday's training session and did not do an awful lot. It would be a blow to lose them because they all performed strongly in the World Cup, but the other side of the coin is that it would be an opportunity for other boys to show what they were all about.

"I really feel for Matthew and his loss is a big blow, but what we have now is strength in depth which gives us options. These are exciting times for Wales. The boys performed exceptionally well in the World Cup; to lose in the semi-final in the manner we did was heart-breaking and we have to get back on track. There was a lot of talk about us at the end of last year just turning up in the Six Nations and winning the grand slam but we do not believe that for one minute. There is a lot of hard work to be done and we have a tough start on Sunday."

Losing Priestland and Roberts, who has not played since before Christmas because of a knee problem, would be keenly felt by Wales. The pair's influence in the World Cup was highlighted by the way they combined in the quarter-final and when Priestland missed the semi-final against France because of a shoulder injury Wales became lateral and slow.

James Hook was the fly-half that night, but a player who played instinctively at 10 when he started his international career was strangely hesitant. His replacement, Steven Jones, was no more assertive, as if the pair had been spooked by the sudden and profitable rise of Priestland.

Hook has been playing at fly-half regularly since the World Cup, having left Ospreys for Perpignan. The Catalan club may be struggling in the Top 14 but the 59-cap Lion says the move has re-energised him and he is confident he would prove an adequate replacement for Priestland should he be required on Sunday.

"The World Cup was so disappointing for me," the 26-year old Hook said. "I worked so hard to be ready for what is the pinnacle of international rugby and it did not go well. The France semi-final was the lowest I have been after a game, without a doubt. I could not think straight for a while and I just wanted to get to France and back out on to the pitch to forget what happened in New Zealand.

"The World Cup is behind me now and I have built up my confidence at Perpignan. The coaches there told me to go out and enjoy my rugby. Perpignan are not where we want to be in the league, but I have settled there with my family. I am looking forward and have trained hard this week: you have to have the mindset that you are going to be playing. It is going to be huge on Sunday. Ireland have quality and experience and we know we are in for a big test."

Wales failed against France not only because their captain, Sam Warburton, was sent off after 19 minutes but because their kickers, Hook, Steven Jones and Leigh Halfpenny, missed four out of five kicks at goal between them. "Stuff happens," Jenkins said. "We had a bad day and it happened to be in a World Cup semi-final, but our overall record in the World Cup was good and we have full confidence in all our kickers. We will decide who will be first-choice in Dublin when the time is right."